Light emitting diodes (LEDs) have a small size and high luminous efficiency so they are often applied to backlight components or being used as emitting pixels in a display device. LEDs in a display are usually driven by a thin-film transistor (TFT). However, transistors in a display inevitably have differences therebetween in threshold voltages (Vth), and the threshold voltage changes as time goes by.
Since the display device adapts many transistor switches to drive LEDs, it is annoying to have the difference in threshold voltage between these transistor switches during the operation of the display device. For example, even when all pixels in an image frame are supplied with the same data voltage, these pixels still have different brightnesses because of the difference in threshold voltage, and thus resulting in a low image quality.
Since the transistors in a display have a great difference in threshold voltage therebetween, it is required to develop a driving method capable of compensating the threshold voltage of a transistors in order to control the LEDs to accurately emit light having a brightness defined by a data voltage.